The present invention relates to a method for controlling a contact pressure with which, in a winding machine during winding, a bobbin to be wound onto a yarn carrier and a roller constructed as a bearing roller, tangential drive roller or grooved drum are pressed against each other, and an apparatus for performing the method.
In the case of a winding machine in which a thread is wound onto a yarn carrier, it is known to drive the bobbin with the aid of a grooved drum or a driving cylinder or roller engaging on the outer circumference of the bobbin. The yarn carrier of the bobbin is normally pivotably mounted in a pivotable or displaceable winding frame. During winding the bobbin engages on the driven roller and by friction contact is rotated by the latter. As the winding of the thread onto the bobbin must permit good unwinding, it is desirable that the driving of the bobbin takes place without slip. It is therefore known to press the bobbin with a specific contact pressure against the bearing roller.
In a known construction the bobbin is arranged above a roller and is held with its yarn carrier in a pivotable winding frame. The winding frame is constructed in such a way that its center of gravity is at a distance from a pivot pin of the winding member so that the weight of the latter presses on the bearing roller. As the bobbin diameter increases the winding member pivots into a position in which the distance between the center of gravity and the pivot pin of the winding member constantly decreases. The consequently constantly decreasing force pressing on the bearing roller as a result of the weight of the winding member, is replaced by the increasing weight of the bobbin. In the case of an even greater bobbin diameter, the center of gravity of the winding member moves from the distance zero towards the pivot pin of the winding member on the opposite side, so that with an increasing bobbin diameter a counterpressure is formed in the sense of relieving the bearing roller of the weight of the bobbin. This makes it possible to control the contact pressure of the bobbin on the bearing roller. However, with this construction the desired contact pressure can only be reached in an approximate manner, because it is dependent on the geometry of the winding frame and the bobbin travel (bobbin shape), as well as the bobbin density.
It is also known to influence the contact pressure of the bobbin on the roller by a counterweight arranged on the winding frame. However, this construction also fails to ensure a precise maintaining of a specific contact pressure.
In a further known construction, the bobbin is arranged laterally in respect to a roller and is pressed onto the latter by springs. For this purpose use is generally made of two oppositely acting spring sets for maintaining the desired contact pressure. However, here again it is only possible to approximately maintain the desired contact pressure.
In yet another known construction, the winding frame is not pivotably mounted about a pivot pin but is instead constructed as a linear guide. If the bobbin is positioned laterally with respect to the roller, then with the aid of a weight guided via a roll, a constant contact pressure of the bobbin on the roller can be achieved. Although admittedly with this construction the desired contact pressure can be precisely maintained, the linear guide represents a relatively complicated and costly solution which makes it difficult to replace the bobbin. It is in particular not possible to arrange the spool or bobbin in a random position with respect to the bearing roller.